1. Field of the Invention
This invention relates a new strain of the fungus Metarhizium anisopliae, compositions thereof, and methods of using the compositions for control of Formosan and other subterranean termites, in particular their alate stage.
2. Description of the Relevant Art
Subterranean termites, including the Formosan subterranean termite (FST), Coptotermes formosanus Shiraki, cause an estimated one billion dollars in prevention and control costs in the United States annually (Potter, M. 1997. In: Handbook of Pest Control, Moreland, D. (Ed.), Mallis G. I. E. Publishing, Cleveland, Ohio, pp. 232-332). The FST is becoming the predominant termite pest species in several southern states and Hawaii. Current FST control methods involve slow-acting, non-repellent termiticides and baits (Su and Scheffrahn. 1998. Integrated Pest Mangt. Rev. 3: 1-13). Insect pathogens are attractive candidates for baiting because of their self-replicating nature and safety to non-target animals. According to Glare and Milner (1991. In: Handbook of Applied Mycology, Vol. 2, Humans, Animals, and Insects, Arora et al. (Eds.), Marcel Dekker Inc., New York, pp. 547-612), the most virulent isolates are those derived from the target insect infected under natural field conditions. Factors that have limited the development of termite biological control agents include: (1) removal of the pathogen by termites by grooming, and (2) isolation of infested members of the colony (Culliney and Grace. 2000. Bull. Entomol. Res. 90: 9-21).
Most studies addressing the conditions required for control of subterranean termites in the field have focused on Metarhizium spp. and Beauveria spp. (Milner et al. 1998b. Australia. Biol. Control 11: 240-247, Sun et al. 2002. J. Invertebr. Pathol. 81: 78-85, Sun et al. 2003a. J. Inverteb. Pathol. 84: 38-46). In addition, Wright et al. (2003. U.S. Pat. No. 6,660,291) have recently patented Paecilomyces spp. for controlling subterranean termites. These Paecilomyces strains are non-repellent, are transferred among termites and cause rapid mortality of termite workers. In the studies of Milner et al. in Australia (1998b, supra), 93 isolates of Metarhizium anisopliae(Metschnikoff), obtained from two species of termites, were tested. Isolate FI-610 was found to be one of the most effective. Successful control of Coptotermes acinaciformis (Froggot) was achieved using direct inoculation with 3×1011 conidia into termite mounds. While it can be difficult to identify the location of an FST nest within a structure, infestations in trees are similar to termite mounds in that they allow localized access, similar to Milner et al., for direct treatment. In addition, biological control agents found to be effective for termite population management can be used alone (Grace, J. K. 2003. Sociobiol. 41: 115-121) or in a synergistic partnership with chemical termiticides (Boucias et al. 1996. Pflanzenschutz-Natrichten Bayer 49: 103-143).
Metarhizium anisopliae(M. anisopliae) is a well known fungal pathogen of a wide range of insect species (Hanel and Watson. 1983. Bull. Ent. Res. 73: 305-313; Rath et al. 1995. Biocontrol Sci. Technol. 5: 439-451; Jones et al. 1996. Environ. Entomol. 25: 481-487; Milner et al. 1998b, supra; Ramakrishnan et al., 1999. J. Econ. Entomol. 92: 1125-1132; Staples and Milner. 2000. Sociobiol. 36: 133-148; Dean et al. 2002. J. Invert. Pathol. 79: 93-101) and, as discussed above, has been used in the control of subterranean termites. An isolate of this fungus, ESC 1, has been commercialized as a mycoinsecticide (BioBlast®) for use in termite control. However, it does not cause high mortality among both FST workers and alates, as shown in the studies of the invention. When allowed to infect FST alates, strain ESC 1 caused only moderate rates of mortality over relatively long periods of time.
Thus there remains a need to obtain effective additional agents for controlling FST alates. Herein we report the isolation of a strain of M. anisopliae, strain C4-B. The C4-B strain causes rapid mortality among both FST alates and FST workers and is thus an effective agent for controlling subterranean termites.